These are bad times for parliament and for all MPs – old, new, red, blue. Britain is unique in the world in that everything flows through parliament – the legislators, the executive, the supreme court, the privy council. In other nations there is a clear constitutional separation of power. A bad head of state or government can be dealt with by an independent congress. Judicial inquiries can deal with corrupt ministers. Legislators properly paid and staffed do not depend on party leaderships for preferment.

In Britain, all is muddled together in the glory of the Commons. It will survive this scandal as it survived earlier scandals or the torpor of the 19th century when it met for less than half the year. The great historian Macaulay wrote that there was nothing "so ridiculous as the British public in one of its periodical fits of morality". The British public is in one of its fits of morality right now but this will pass.

There may be a terrible consequence as for the first time Britain elects anti-semitic racists in the form the BNP as European parliamentary representatives on 4 June. That is why many of us are saddened that instead of focusing on what needs to be done now, this week, this day to clean up the mess, our party leaders seem like rabbits blinded in headlights. They condemn each other and something called "the system" instead of sitting down together in this hour of parliamentary crisis and finding a way forward.

How do you fit into all this? Let me make clear that if you are to be criticised for not doing anything to change the system then the same criticisms have to be made against all of your predecessors as Speakers. They did not lift a little finger to change exactly the same "system" – namely MPs having a tax-free allowance to pay for second homes. I do not recall Speaker Boothroyd or Speaker Weatherall challenging the second homes allowance system, nor any of the deputy speakers nor for that matter any Prime Minister or Leader of the Oppostion.

Now we are wiser. But it is sheer hypocrisy to blame you and you alone when all previous Speakers were happy to go along with the "system".

Are you a good Speaker? I don't know. I saw you being kind and helpful to a new generation of MPs who entered the House in 1997, especially young women who felt oppressed by the male and small-c conservative nature of the Commons. You had to deal with invasions of the Commons permitted by Conservatives obsessed with fox-hunting and oversee the installation of ugly new security systems as a result of global terrorism.

I have never been happy at how you cut me off whenever I have sought to use Question Time to challenge the anti-Europeanism of David Cameron and William Hague. You shut me up, saying I should not do politics at Question Time, but if an MP cannot do politics what can we do? I remember David Cameron lifting his eyes to the heavens as you stopped me having a go at him on Europe because the one thing the Conservative leader can do is defend himself at the despatch box. But I accepted your ruling as we all do.

I have attacked the snobs who have mocked you for your Glasgow accent and the fact you are not the kind of public school ex-minister who previously became Speaker. I am not sure you were right on Damian Green but he and David Cameron have yet to come clean on the Tory Party's effort to suborn a civil servant sworn to protect the confidentiality of the home secretary's private office. The refusal of the party leaders and their whips to cooperate in sorting out pay and allowances has left you in an impossible position. Everyone can attack you or brief against you while refusing to accept their own responsibilities. I am nervous of the constant attacks by Douglas Carswell MP. I respect his integrity but when a Conservative Speaker comes along who makes mistakes we will see opposition attacks on him. So Mr Carswell, who has not been rebuked by David Cameron, has set a dangerous precedent in attacking the Chair of the Commons and not the party machines that failed to clean up a rotten "system".

But I now believe you should make your intention clear not to seek a third term as Speaker. You will have served as long as most Speakers. You can stay as an MP and all your friends will be there in the Tea Room at both the Labour and Tory ends of it to share a cup of tea and a story. I say this to you as I consider it important that the current House elects your successor. After the next election, I believe we will see as many as half if not more current MPs being replaced. New MPs will know nothing of potential speaker candidates whereas, for good or ill, we know the qualities or lack thereof of current MPs from whom a new Speaker has to be chosen. The ballot, thank God, is secret so pressure from party leaders and whips can have little influence, and they would be better advised putting swiftly in place a new structure for pay and allowances that can withstand all public scrutiny.

I do not know who is the Solomon, the Solon, the Lincoln or the Mandela among our midst who can take over. But let someone be chosen. You will step down with honour and thanks from MPs and the nation. Please announce your decision soon so that before the summer is out we can have a new Speaker in place.